MXF with Embedded Captions - First Caption Cut Off + Video Break Up

I've found many other posts mentioning issues with embedded captions in an MXF file, but none of them seem to mention the problem I'm having.

I'm running Premiere Pro v 22.2.0 on a Mac Studio running MacOS Monterey 12.6. Any newer versions of PrPro cause frame substitution errors every 5 minutes during playback and even more frequently on export.

I'm exporting to MXF OP1a XDCAM HD 50 NTSC 60i

I can successfully output an MXF with embedded 608 captions

I've attached images of my timeline before export, as well as the exported file re-imported and dropped on the timeline next to the original sequence, my sequence 

settings, and my export settings (video and caption tabs).

The broadcaster wants a blank caption after the slate with a duration of 10 frames starting at 5 frames, and another 10 frame blank caption at the end. Those are the two tiny captions you see near the beginning and at the end.

The problem is that the first caption after that gets cut off. It's supposed to start immediately after the first blank caption but it starts 74 frames later than it should. The red arrows in my screen shot highlight the discrepency.

The broadcaster has rejected the file becuase of the caption issue, and they also say that there are video breakups throughout. Using Media Encoder to output gives the same result. I've tried all the variations of ticking and unticking Force Fixed-length GOPs and Force Closed GOPs with no improved results.

Any ideas?